1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and more particularly, to a semiconductor device which is resin-encapsulated in a semiconductor wafer state and a method of fabricating the semiconductor device. Thus, the invention deals with such a semiconductor device as described above having high reliability for interconnection with a substrate and a method of fabricating the semiconductor device.
2. Description of the Related Art
Portable equipment has lately come into widespread use at a rapid pace, and this has been accompanied by increasing demands for semiconductor devices mounted therein, which are thinner, smaller in size, and lighter in weight than conventional ones. A number of packaging technologies have been proposed in order to cope with such demands.
As one of such technologies, a chip size package (referred to hereinafter as CSP) equivalent or substantially equivalent in size to a semiconductor chip with an integrated circuit formed thereon has been developed.
There has been available a conventional CSP wherein rewiring conductors made of Cu, which are connected to each of the electrode pads of a semiconductor chip, are formed. Terminals called posts, which are connected to the rewiring conductors, are formed for the purpose of essentially re-locating or redisposing the electrode pads. The surface of the semiconductor chip is encapsulated with resin to the height of the terminals, and metallic electrodes such as solder balls etc. are provided at the tip of each of the terminals, exposed out of the resin.
In a method of fabricating the CSP, a polyimide layer is first formed over a semiconductor wafer. A rewiring pattern made of Cu, connected to electrode pads of a plurality of semiconductor chips formed on the semiconductor wafer, is formed. Terminals called posts, connected to respective rewiring conductors, are also formed, thereby essentially redisposing the electrode pads. Subsequently, the entire surface of the semiconductor wafer with the terminals formed thereon is resin-encapsulated, and after curing of the resin, it is abraded to the extent that the tips of the respective terminals are exposed. Furthermore, the exposed tip of each of the terminals is provided with a metallic electrode such as a solder ball etc. before dicing the semiconductor wafer into separated pieces for individual semiconductor chips.
However, when a temperature cycle test is repeatedly conducted on such a CSP as described above after it is mounted on a substrate, there arises a possibility of cracks occurring at the metallic electrodes (such as the solder balls etc.) This is attributable to a large difference in thermal expansivity between the CSP and the substrate, which results in concentration of stress at a bonding portion between the metallic electrode and the post. An alternative cause may be a small area of bonding between the respective metallic electrodes and the respective terminals of the CSP due to a narrow spacing between the terminals, which results in a reduced bonding force between the metallic electrode and the post.